Abstract
BackgroundRecent WHO guidelines identify virologic monitoring for diagnosing and confirming ART failure. In view of this, validation and scale up of point of care viral load technologies is essential in resource limited settings.MethodsA systematic validation of the GeneXpert® HIV-1 Quant assay (a point-of-care technology) in view of scaling up HIV-1 viral load in India to monitor the success of national ART programme was carried out. Two hundred nineteen plasma specimens falling in nine viral load ranges (<40 to >5 L copies/ml) were tested by the Abbott m2000rt Real Time and GeneXpert HIV-1 Quant assays. Additionally, 20 seronegative; 16 stored specimens and 10 spiked controls were also tested. Statistical analysis was done using Stata/IC and sensitivity, specificity, PPV, NPV and %misclassification rates were calculated as per DHSs/AISs, WHO, NACO cut-offs for virological failure.ResultsThe GeneXpert assay compared well with the Abbott assay with a higher sensitivity (97%), specificity (97-100%) and concordance (91.32%). The correlation between two assays (r = 0.886) was statistically significant (p < 0.01), the linear regression showed a moderate fit (R2 = 0.784) and differences were within limits of agreement. Reproducibility showed an average variation of 4.15 and 3.52% while Lower limit of detection (LLD) and Upper limit of detection (ULD) were 42 and 1,740,000 copies/ml respectively. The misclassification rates for three viral load cut offs were not statistically different (p = 0.736). All seronegative samples were negative and viral loads of the stored samples showed a good fit (R2 = 0.896 to 0.982).ConclusionThe viral load results of GeneXpert HIV-1 Quant assay compared well with Abbott HIV-1 m2000 Real Time PCR; suggesting its use as a Point of care assay for viral load estimation in resource limited settings. Its ease of performance and rapidity will aid in timely diagnosis of ART failures, integrated HIV-TB management and will facilitate the UNAIDS 90-90-90 target.
Highlights
Recent WHO guidelines identify virologic monitoring for diagnosing and confirming antiretroviral therapy (ART) failure
Study design A systematic validation of the GeneXpert® Human immunodeficiency virus (HIV)-1 Quant assay in view of scaling up HIV-1 viral load in India to monitor the success of national ART programme was carried out
The paired plasma specimens collected from 219 study participants were tested by Abbott m2000 Real Time PCR and GeneXpert HIV-1 Quant assays
Summary
Recent WHO guidelines identify virologic monitoring for diagnosing and confirming ART failure. Nucleic Acid Testing (NAT) based technologies are considered as the gold standards for HIV-1 viral load estimation because of their high specificity, sensitivity and wide linear range of detection. These assays require testing to be performed by well-trained technicians and need at least 8-10 h. Due to minimal requirement of infrastructure, it is very easy to scale up the activity of viral load testing nationally Considering all these features, the Gene Xpert HIV-1 Quant assay serves as a valuable point of care viral load assay that could be useful for monitoring antiretroviral therapy as well as integrated HIV-TB management in developing countries like India [23]. The performance evaluation of this new assay will ensure its decentralized utility in the clinical set up and will assist in management of patient care efficiently
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